Synthetic data collection method for full matrix capture using an ultrasound array

ABSTRACT

A method for efficiently achieving full-matrix ultrasonic data capture which includes the steps of providing an ultrasound array apparatus, the ultrasound array apparatus further comprising a probe, collecting data over a plurality of inspection locations, generating a plurality of data matrices, each of the data matrices reflecting data collected at the locations, and collecting, initially, a subset of a quantity of data needed for reconstruction of each of the inspection locations. In the method, as the probe moves from collection location to collection location, a data matrix at a prior collection location is gradually filled in as the probe moves to subsequent collection locations. In certain embodiments physical scanning of a probe with few elements is replaced by electronically scanning using an array with many elements.

FIELD AND BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of data collection,and in particular to a new and useful method for achieving full matrixcapture and processing of waveform data by employing an ultrasound arrayapparatus.

2. Description of the Related Art

In ultrasonic testing, very short ultrasonic pulse-waves with centerfrequencies ranging typically from 0.1 to 15 MHz and, occasionally, upto 50 MHz are launched into materials to detect internal flaws or tocharacterize materials. The technique is also commonly used to determinethe thickness of a tested object, for example, to monitor pipe wallcorrosion.

Ultrasonic testing is often performed on steel and other metals andalloys, though it can also be used on concrete, wood and composites,albeit with lower resolution. It is a form of non-destructive testingused in many industries.

Two basic methods of receiving the ultrasound waveform are pulse-echoand pitch-catch. In pulse-echo mode the transducer performs both thesending and the receiving of the pulsed waves as the “sound” isreflected back to the device. The reflected ultrasound comes from aninterface such as the back wall of the object or from an imperfectionwithin the object. The diagnostic machine typically displays theseresults in the form of a signal with amplitude representing intensity ofthe reflection and arrival time of the reflection representing distance.In pitch-catch mode separate transducers are employed to transmit andreceive the ultrasound.

There are a number of benefits to ultrasound testing. This testingmethod provides high-penetrating power, which allows the detection offlaws deep in the part being analyzed. It is also a high sensitivityform of testing, permitting the detection of extremely small flaws.Generally only one surface needs to be accessible for ultrasoundtesting. The method provides greater accuracy than other nondestructivemethods in determining the depth of internal flaws and the thickness ofparts with parallel surfaces. It provides some capability of estimatingthe size, orientation, shape and nature of defects. It is generallynonhazardous to operations or to nearby personnel and has no effect onequipment and materials in the vicinity. It is also capable of portableas well as highly-automated operation.

One type of ultrasound testing is known as phased array ultrasound. Forthis type of testing the probe(s) are comprised of a plurality (array)of elements, each of which can transmit and/or receive ultrasoundindependently. By combining the transmitted waves from each individualelement a composite sound beam is created. This beam may be steeredand/or focused in an arbitrary manner by applying short time delaysacross the elements and then firing the elements together. In ananalogous manner a receive array may be set to be sensitive to incomingultrasound from a particular angle and/or focal depth by applying a setof short delays across elements and subsequently adding togethercontributions from all elements.

Matrix capture of ultrasonic information is a powerful technique forinspection which uses the same array probes as phased array ultrasound.The method is distinct, however. Matrix capture is achieved, forexample, by firing each array element in succession and recording thereceived waveforms at all elements for each firing. The resultingcollected data at a given inspection location forms a matrix ofwaveforms for which each waveform is associated with onetransmit-receive element pair. By acquiring all data for everytransmit/receive element pair over the array, virtual ultrasonic scansat arbitrary angles can be reconstructed at any time after data has beencollected by applying the appropriate set of short delays to therecorded waveforms and then adding all signals together (using acomputer, for instance).

Matrix capture is identified as distinct from phased array in thefollowing manner. In the phased array method, at a given inspectionlocation the appropriate set of short delays is applied to all waveformsduring transmit and receive phases, and at that time waveforms from allarray elements are summed together. Only the final result is stored. Inthe matrix capture method all waveforms corresponding to everycombination of transmit and receive element at each inspection locationare stored in a data matrix. At any subsequent time in post-processingthe appropriate set of short delays are applied to the stored waveformsand all waveforms in the matrix are summed together in order toeffectively create a steered and/or focused beam of ultrasound.

Known matrix capture techniques, however, have an inherent andsignificant disadvantage, namely the need for storing a large amount ofdata. All waveforms for all transmit/receive pairs must be stored forevery scan location.

By way of an illustration, each waveform typically requires 1000 timepoints to be collected, each point requiring one byte. For a 32-elementarray this means that (32)², or 1024, waveforms must be collected. At1000 bytes each, this collection results in 1 MB of data stored for eachscan location. Even a small scan will require on the order of 100 times100, or 10,000, scan locations. This collection of data will result intotal data storage of about 10 GB. For the case of a pulse-echoinspection with a probe containing m elements the number of waveformsthat must be collected per scan location, including reciprocityconsiderations, is:

${{Number}\mspace{14mu} {of}\mspace{14mu} {waveforms}\mspace{14mu} {per}\mspace{14mu} {inspection}\mspace{14mu} {{location}\left( {{pulse}\text{-}{echo}} \right)}} = {\frac{m \cdot \left( {m + 1} \right)}{2}.}$

This requirement strains data storage needs, and also can place apractical limitation on scan speed because it can be difficult torapidly move so much data.

Gains in efficiency can be realized by a method in which scan and/orindex increments are set equal to element pitch or unit fractionsthereof. In this case a large fraction of the collected data at onelocation is (theoretically) identical with data collected at neighboringlocations.

One illustrative example involves a situation in which the array probeis operating in pulse-echo mode and has three elements. The probe willbe moved to three separate positions along the same direction as theultrasonic array. At any given position, in order to accumulate datafrom all transmit-receive pairs with a standard method of data capturethen

$\frac{m \cdot \left( {m + 1} \right)}{2} = {\frac{3 \cdot 4}{2} = 6}$

waveforms must be recorded. Additionally, each of the three elementsmust be fired once. In order to collect all data for the three probepositions a total of 9 element firings are needed and 18 waveforms mustbe collected.

This situation is illustrated in FIG. 1, in the section marked “StandardData Collection.” A set of tables are shown, each representing the datamatrices for a probe at subsequent inspection locations (shown in theupper left) corresponding to a 3-element array moving in increments ofone element pitch. Tables from left to right represent data matriceswhich need to be filled in each subsequent location (A, B, C). Tablesfrom top to bottom represent these same arrays at subsequent probelocations (A, B, C). The data required at each location is a set ofwaveforms corresponding to each transmit-receive pair. The letters inthe tables represent the probe location at which data is collected. Forstandard collection, at each probe location (A, B, and C), all data forreconstruction at that respective location is collected.

In the case where the probe is moved along the array direction at a stepsize equal to the element pitch, if the elements are fired 9 times and18 waveforms are collected then much of the data is redundant.

Thus, a need exists for a method of capture of waveform data that isefficient and overcomes the above deficiencies, including, but notlimited to, redundancies and strain on storage capacity.

SUMMARY OF THE INVENTION

The present invention addresses known deficiencies in the art and isdrawn to a new and efficient method of data collection that effectivelyemploys ultrasound technology.

Accordingly, one aspect of the present invention is to provide a meansfor achieving full matrix capture by efficiently employing an ultrasoundarray apparatus.

Embodiments of the present invention provide a method for efficientlyachieving full-matrix ultrasonic data capture which includes the stepsof providing an ultrasound array apparatus, the ultrasound arrayapparatus further comprising a probe, moving the probe over a pluralityof collection locations, generating a plurality of data matrices, eachof the data matrices reflecting data collected at the locations, andcollecting, initially, a subset quantity of data needed forreconstruction of each of the collection locations. In the method, asthe probe moves from one collection location to the next, a data matrixat a prior collection location is gradually filled in as the probe movesto subsequent collection locations.

Accordingly, one aspect of the present invention is drawn to a methodfor efficiently achieving full-matrix ultrasonic data capturecomprising: (a) providing an ultrasound array apparatus, the ultrasoundarray apparatus comprising a probe, the probe adapted for positioningover a test piece; (b) collecting data over a plurality of locations;(c) generating a plurality of data matrices, each of the data matricesreflecting data collected at the locations; (d) collecting, initially, asubset of a quantity of data needed for reconstruction at each of thelocations; and (e) collecting data from location to location, graduallyfilling in a data matrix at a prior location as the probe moves tosubsequent locations.

Accordingly, another aspect of the present invention is drawn to amethod for efficiently achieving full-matrix ultrasonic data capturecomprising: (A) providing a two-dimensional ultrasound array apparatus,the ultrasound array apparatus comprising a probe, the probe adapted forscanning and the probe comprising scan increments and nominal scanboundaries; (B) moving the probe over a plurality of inspectionlocations; (C) generating a plurality of data matrices, each of the datamatrices reflecting data collected at the inspection locations; (D)collecting, initially, a subset of a quantity of data needed forreconstruction at each of the inspection locations; and (E) as the probemoves from inspection location to inspection location, gradually fillingin a data matrix at a prior inspection location as the probe moves tosubsequent inspection locations.

Inspection locations may correspond to collection locations but are notnecessarily the same. For example, if only sparse coverage is required(e.g. for component thickness mapping) then inspection locations maycorrespond to some subset of collection locations.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich a preferred embodiment of the invention is illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a composite schematic illustration of how an array probeoperating according to the present efficient data collection methodcompares with standard data collection;

FIG. 2 is an illustration of a two-step process specific to a“pitch-catch” probe arrangement where at each collection location, inaddition to the transmit element firing, the opposing element from the“catch” probe also transmits a signal and all elements from the“transmit” probe (save for the one which originally transmitted) collectthe receive signals; and

FIG. 3 is an illustration of a configuration for a two-dimensionalultrasonic array, including a representation of array indices as well asorientation with respect to scan and index axes.

DESCRIPTION OF THE EMBODIMENTS

Referring now to the drawings, FIG. 1 illustrates, in the sectionidentified as “Efficient Data Collection,” the present, novel ultrasounddata collection method. Following the “Standard Data Collection” method,in order to collect all data for the three probe positions a total of 9element firings would be needed and 18 waveforms must be collected.According to the present “Efficient Data Collection” method only 5element firings and 12 waveforms need to be collected in order to haveall waveform data at all positions. In order for this particularimplementation to be possible the probe increment must be equal toelement pitch. Also, this particular implementation relies on thereciprocity principle (i.e. a signal transmitted by element x andreceived by element y is in principle the same as a signal transmittedby element y and received by element x). In the case of pulse-echooperation the consequence of the reciprocity principle is that thematrix is symmetrical about its diagonal; i.e. element xy is equal toelement yx. At each probe location only one element is fired and allelements receive. As a result, a subset of the data needed forreconstruction at that location is collected. As the probe moves fromposition A to B to C, the data matrix at location A is gradually filledin. While only three firings are shown, as the probe continues to movethe data matrices for locations B and C will be filled as well.Considering, for example, the data matrix at location A: as the probemoves, data from locations A, B, and C are all used to enablereconstruction at that point.

The advantage in efficiency provided by embodiments of the presentinvention increases as the number of elements and positions increases.For k positions along an inspection line and m elements, number offirings needed and waveforms to be collected are expressed below as

Number of firings (pulse-echo)=(k+m−1), and

${{Number}\mspace{14mu} {of}\mspace{14mu} {waveforms}\mspace{14mu} {{needed}\left( {{pulse}\text{-}{echo}} \right)}} = {\left( {k \cdot m} \right) + {\frac{m \cdot \left( {m - 1} \right)}{2}.}}$

So, in the situation in which a 32-element array is used and 100 datapoints are taken along a scan line, only 3,696 waveforms will need to becollected and only 131 element firings will be needed. This comparesvery favorably to the (32×33/2)×100=52,800 waveforms that would need tobe collected from 3200 firings in the absence of the presently-claimedinvention, which takes advantage of data redundancy.

If the probe increment is set to a unit fraction of element pitch thenthe procedure outlined in paragraph 20 may still be applied. In the casethat probe increment is equal to element pitch divided by L, thenconceptually L arrays may be created and data will be collected for eachone in turn every L scan increments. In order to fill all data matricescompletely the number k of inspection locations must be evenly divisibleby L. Then, for a total of k positions the number of firings necessaryand number of waveforms needed are expressed in the equations below as:

Number of firings (increment is unit fraction of pitch)=k+L·(m−1), and

${{{Number}\mspace{14mu} {of}\mspace{14mu} {{waveforms}\left( {{increment}\mspace{14mu} {is}\mspace{14mu} {unit}\mspace{14mu} {fraction}\mspace{14mu} {of}\mspace{14mu} {pitch}} \right)}} = {\left( {k \cdot m} \right) + {L \cdot \frac{m \cdot \left( {m - 1} \right)}{2}}}},$

where k>L for both of the above equations.

If the inspection is performed using a pitch-catch arrangement then asecond step is required in order to complete the subset of data thatmust be collected at each location. Elements normally arranged asreceivers must be adapted as transmitters as well, and converselyelements arranged as transmitters must be arranged as receivers as well.At each collection location, in addition to the transmit element firingthe opposing element from the “catch” probe must also transmit a signaland all elements from the “transmit” probe (save for the one whichoriginally transmitted) must receive the signals. This procedure isrepresented in FIG. 2 as a two-step process. In this manner thesub-array will be filled and collection may proceed as outlined inparagraph 20. If this arrangement is made then the total number offirings needed and total number of waveforms needed are expressed in theequations below as

Number of firings (pitch-catch)=2(k+m−1)−1, and

Number of waveforms collected (pitch-catch)=k(2m−1)+(m−1)².

In certain embodiments scan increment is equal to element pitch. Inthese embodiments an alternative to moving the probe along the directionof the array is to make a probe with many elements and generate atransmit and receive sequence which is equivalent to moving a smallerprobe. While this requires the construction of a large array, itprovides the advantage of potentially eliminating moving parts andpositioning errors.

Embodiments of the present invention may also be applied in the contextof two-dimensional arrays, for which gains in data storage and firingefficiency can be even more dramatic. In fact, without application ofthe present, novel method to improve efficiency it is likely that matrixfiring would be impractical to implement for all but the smallesttwo-dimensional arrays using computer technology available today. Forexample, consider the situation of a 16-element x 8-element array probeoperating in pulse echo mode. Without implementation of such a techniqueto improve efficiency, (16×8)=128 firings would be needed at each probeposition in order to obtain the (128×129)/2=8256 waveforms. Assuming1000 one-byte points per waveform and an array of 100 by 100 probepositions, this leads to a total data storage size of 82 GB.

By re-using data collected at different probe positions the presentinvention provides a very considerable savings in number of firings anddata collection. Consider a raster scan along both array directions fora two-dimensional array with n elements along the scan direction and melements along the index (or step) direction. The raster scan includes kcollection locations along the scan direction and l steps. Anillustration of this arrangement is provided in FIG. 3. For the(n×m)-element ultrasonic array operating in pulse-echo mode only m or nfirings (whichever is smaller) are needed and (n·m)+(n−1)·(m−1)waveforms need to be stored at each collection location. Thiscorresponds to firing the corner element (i.e., element (1,1)) andreceiving on all elements, then firing each element along the short edgeof the array in turn (e.g., elements (M,1) for M=2 through m) and, foreach firing, receiving on all elements along the long edge of the array(e.g., elements (1,N) where N=2 through n). (Additional waveforms willneed to be recorded in order to fill data matrices near edges of theinspection grid). In one embodiment the probe will be scanned beyond thenominal scan boundaries and data will be taken such that data matricesnear the boundaries are filled. The distance the probe is scanned beyondthe scan boundaries is equal to the number of elements along eachrespective dimension minus one. Thus, if there are k scan points alongthe “n” dimension of the probe and l scan points along the “m” dimensionof the probe, a conservative estimate of the total number of waveformsneeded is shown below:

Number of waveforms (2D array)≈(k+n−1)·(1+m−1)·[n·m+(n−1)·(m−1)].

This approximate formula is an overestimate of the total number ofwaveforms needed because fewer than [(n·m)+(n−1)·(m−1)] waveforms willneed to be collected at scan locations near the edges of the grid inorder to provide a full reconstruction over the k by l grid. However, itis sufficient to demonstrate the advantage of use of this novelcollection method in order to reduce data storage requirements.Returning to the 16×8 array example, this means that only 8 firings arenecessary at each probe position and 233 waveforms need to be stored.For the same 100 by 100 array of probe positions this leads to totaldata storage of approximately (115·107·233)·1000 bytes equalsapproximately 3 GB which is easily achievable using the technologycurrently known in the art.

In another embodiment of the present invention, as it pertains totwo-dimensional arrays, symmetry is exploited only along the indexdirection. This may be done for a variety of reasons. As examples, ifpositioning along the index direction cannot be performed withsufficient precision, or if the index increment cannot be set equal toelement pitch along that direction, or if the scan is performed alongonly one direction, then symmetry cannot be exploited along the indexdirection. In this case significant gains can still be made byimplementing the following procedure: at each scan location, all melements for which N=1 (i.e. element (M,1) where M=1 through m) arefired in turn, and for each firing all received waveforms from allelements in the array are recorded. (Note that, when firing element(s)(M,1) where M>1, waveforms at elements (M′,1) where M′<M does not needto be recorded because reciprocity considerations render it redundant.)At each scan location m firings are thus required and

$\left\lbrack {\left( {m^{2} \cdot n} \right) - \frac{m\left( {m - 1} \right)}{2}} \right\rbrack$

waveforms must be recorded. Extra waveforms will need to be recorded atlocations beyond the nominal scan grid in order to record all waveformsneeded to fill all matrices at every scan location. An estimate of thetotal number of waveforms needed for a scan over k by l locations is:

Number of waveforms (2D array, symmetry exploited only

$\left. {{along}\mspace{14mu} {scan}\mspace{14mu} {direction}} \right) \approx {\left( {k + n - 1} \right) \cdot l \cdot {\left\lbrack {\left( {m^{2} \cdot n} \right) - \frac{m \cdot \left( {m - 1} \right)}{2}} \right\rbrack.}}$

This estimate is slightly conservative because it does not account forthe reduced number of waveforms which need to be collected at locationsbeyond the nominal range k. Returning to the example of a 16×8 arraywith 100×100 scan locations, the total data which needs to be stored isapproximately (115·100·996)·1000 bytes equals 11.45 GB. This is still avery considerable improvement over the storage requirement of 82 GBwhich is required using the standard collection methodology.

The present invention provides at least three advantages. The first isreduction of data storage. This allows more files to be stored on asingle drive and also allows the ability in some cases to put all scandata into system memory, which would allow instantaneous access to allscan data. The second is potential for dramatically increased scanspeed. Since less data is being acquired at each position, datathroughput is reduced considerably. This increase in scan speed canresult in reduced inspection costs. The third advantage is the potentialfor cleaner data because fewer transmitter firings results in a longertime interval between firings, which means that the sound has more timeto dissipate.

Alternatives to the present efficient data collection method involvecollecting the full set of data at every scan location. This methodresults in slower scan times, potentially noisier data, and greatlyincreased (and in some cases impractical) storage requirements.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:
 1. A method for efficiently achieving full-matrixultrasonic data capture comprising: (a) providing an ultrasound arrayapparatus, the ultrasound array apparatus comprising a probe, the probeadapted for positioning over a test piece; (b) collecting data over aplurality of locations; (c) generating a plurality of data matrices,each of the data matrices reflecting data collected at the locations;(d) collecting, initially, a subset of a quantity of data needed forreconstruction at each of the locations; and (e) collecting data fromlocation to location, gradually filling in a data matrix at a priorlocation as the probe moves to subsequent locations.
 2. The method ofclaim 1, wherein the ultrasonic array has k positions and m elements andno more than (k+m−1) element firings are required and no more than$\left( {k \cdot m} \right) + \frac{m \cdot \left( {m - 1} \right)}{2}$wavetorms are required to be collected in order to collect all the dataneeded for reconstruction.
 3. The method of claim 1, wherein the probehas a plurality of elements, each of the elements having an elementpitch, further comprising the step of setting the scan increment equalto element pitch.
 4. The method of claim 1, wherein the probe is movedalong a direction of the ultrasonic array to generate the plurality ofdata collection locations.
 5. The method of claim 3, wherein a largearray is employed.
 6. The method of claim 5, wherein collection of dataover the plurality of locations is accomplished by electronicallytransmitting and receiving on a subset of the elements, thenincrementing the subset in order to electronically increment the datacollection location.
 7. The method of claim 1, wherein the ultrasoundarray is operating in pitch-catch mode.
 8. The method of claim 7,wherein the array has k positions and m elements and a subset oftransmit elements and a subset of receive elements are fired in order tofill the matrix at each position.
 9. The method of claim 8, wherein nomore than 2(k+m−1)−1 firings are required and no more thank(2m−1)+(m−1)² waveforms are required to be collected in order tocollect all the data needed for reconstruction.
 10. The method of claim1, wherein data collection increment is a unit fraction of element pitchsuch that collection increment is equal to pitch divided by L.
 11. Themethod of claim 10, wherein the array has k positions and m elements andno more than k+L·(m−1) element firings are required and no more than$\left( {k \cdot m} \right) + {L \cdot \frac{m \cdot \left( {m - 1} \right)}{2}}$waveforms are required to be collected in order to collect all the dataneeded for reconstruction, with the proviso that k>L for both of theequations herein.
 12. The method of claim 1, wherein the collected datais reused.
 13. A method for efficiently achieving full-matrix ultrasonicdata capture comprising: (A) providing a two-dimensional ultrasoundarray apparatus, the ultrasound array apparatus comprising a probe, theprobe adapted for scanning and the probe comprising scan increments andnominal scan boundaries; (B) moving the probe over a plurality ofinspection locations; (C) generating a plurality of data matrices, eachof the data matrices reflecting data collected at the inspectionlocations; (D) collecting, initially, a subset of a quantity of dataneeded for reconstruction at each of the inspection locations; and (E)as the probe moves from inspection location to inspection location,gradually filling in a data matrix at a prior inspection location as theprobe moves to subsequent inspection locations.
 14. The method of claim13, wherein the two-dimensional ultrasound array apparatus has two arraydimensions, an array dimension m along the index axis and an arraydimension n along the scan axis.
 15. The method of claim 14, wherein thearray is operated in pulse-echo mode.
 16. The method of claim 13,wherein at each collection location only the smaller of m or n firingsare required and no more than [(n·m)+(n−1)·(m−1) waveforms are requiredto be stored in order to collect all of the data needed forreconstruction.
 17. The method of claim 14, wherein the probe is scanneda predetermined distance beyond the nominal scan boundaries and thequantity of data is collected such that data matrices of the pluralityof data matrices near the nominal scan boundaries are filled.
 18. Themethod of claim 17, wherein each of the dimensions has a number ofelements along a length thereof, and wherein the distance the probe isscanned beyond the nominal scan boundaries is equal to the number ofelements along each respective dimension minus one.
 19. The method ofclaim 14, wherein there are k scan points along the n dimension and 1index, or step, points along the m dimension.
 20. The method of claim19, wherein no more than (k+n−1)·(1+m−1)·[n·m+(n−1)·(m−1)] waveforms arerequired to fill all of the data matrices.
 21. The method of claim 19,wherein symmetry is exploited only along the scan axis and no more thanm firings are required at each collection location and no more than$\left( {k + n - 1} \right) \cdot l \cdot \left\lbrack {\left( {m^{2} \cdot n} \right) - \frac{m \cdot \left( {m - 1} \right)}{2}} \right\rbrack$waveforms are required to fill all of the data matrices.